重新打开由宝石提供的ActiveRecord模型 [英] Re-open an ActiveRecord model that's provided by a gem

问题描述

我试图扩展一个ActiveRecord模型（ Vote ）一个gem（ https://github.com/peteonrails/vote_fu ）提供给我的应用程序。 （即， app / models 中没有 vote.rb ）

我的第一个方法是创建一个名为 lib / extend_vote.rb 的文件，其中包含以下代码：

  Vote.class_eval do 
 after_create：create_activity_stream_event 
 has_one：activity_stream_event 
 
 def create_activity_stream_event 
＃something .. 
结束
结束
  

这在创建第一张投票时有效，但当我尝试创建每个后续投票我得到错误 TypeError（不能重复NilClass）。

我认为这个错误是这是由于在每个请求后自动重载 Vote 类，但是 lib / extend_vote.rb 仅在服务器启动时加载一次，这会导致 has_one：activity_stream_event 关联表现异常。 （此外，如果我在 development.rb 中设置 config.cache_classes = true ），问题就消失了。

为了解决这个问题，我试图通过向我的<$ c添加一个 to_prepare 块来重新加载投票扩展$ c> development.rb ：

  config.to_prepare do 
 load'extend_vote。 rb'
 end 
  

解决了（can not dup NilClass）问题，但现在无论何时创建新投票，都会调用 create_activity_stream_event 回调函数。也就是说，第一次投票调用它一次，第二次调用它两次，等等等等。所以看起来像 to_prepare 块正在积极地重新加载扩展TOO并添加重复的回调。

为这个投票模型添加方法和回调的最佳方式是什么？

我相信您可以使用 ActiveSupport :: Concern 来阻止模块的存在包括由几次回调导致的几次。
请参阅下面的示例：

  module VotePatch 
扩展ActiveSupport :: Concern 
 
包含
 after_create：create_activity_stream_event 
 has_one：activity_stream_event 
 end 
 
模块InstanceMethods 
 def create_activity_stream_event 
＃您的代码在这里
结束
结束
 
结束
 
 Vote.send（：include，VotePatch）
  

I'm trying to extend an ActiveRecord model (Vote) that a gem (https://github.com/peteonrails/vote_fu) provides to my application. (I.e., there is no vote.rb in app/models)

My first approach was to create a file called lib/extend_vote.rb that contains the code:

Vote.class_eval do
  after_create :create_activity_stream_event
  has_one :activity_stream_event

  def create_activity_stream_event
    # something..
  end
end

This works when the first vote is created, but when I try to create each subsequent vote I get the error TypeError (can't dup NilClass).

I think this error is caused by the fact that the Vote class is reloaded automatically after every request, but the code in lib/extend_vote.rb is loaded only once when the server starts and this causes the has_one :activity_stream_event association to behave weirdly. (Also, the problem goes away if I set config.cache_classes = true in development.rb)

To solve this problem, I tried to make the vote extensions reload on every request by adding a to_prepare block to my development.rb:

config.to_prepare do
  load 'extend_vote.rb'
end

This solves the (can't dup NilClass) problem, but now whenever I create a new vote, the create_activity_stream_event callback gets called an additional time. I.e., the first vote calls it once, the second calls it twice, etc, etc. So it seems like the to_prepare block is reloading the extension TOO aggressively and adding duplicate callbacks.

What's the best way to add methods and callbacks to this Vote model?

解决方案

[UPDATE: should be the right solution to prevent the module being include several times in the same class]

I believe you can use ActiveSupport::Concern to prevent the module being include several times which result by callback called several time. See the example below :

module VotePatch
  extend ActiveSupport::Concern

  included do
    after_create :create_activity_stream_event
    has_one :activity_stream_event
  end

  module InstanceMethods
    def create_activity_stream_event
      #your code here
    end  
  end

end

Vote.send(:include, VotePatch)

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